Little spots of less density in 4x5 negs, but they are not dust
So I have these little spots of less density in some of 4x5 negs lately. They aren't completely clear clear like dust would be and have been happening in clear skies. Did I get an iffy batch box of Tri-X or is there some chemical process that could cause this. Could too strong a stop bath be the culprit or leaving it in a permawash too long cause something like this. I'd like to avoid it if possible. I thought maybe it was drying marks also, but am using distilled water and LFN. Anyhow, as always thanks in advance and you guys are the best!
The readers have no photos to guide their thinking. My first inclination that fits your description of the problem is air bubbles adhering to the emulsion. These insulate the emulsion during some part of the development, shortening the total development time compared to the surrounding area that wasn’t covered with an air bubble.
Since modern film has such a thin emulsion (usually on the order of 0.0005” to 0.0007”), transferring the film into a tray of water after the developing step instantly dilutes the miniscule amount of retained developer so that development comes to a screeching halt. Therefore, stop bath is not needed for film. Stop bath won’t hurt, but is unnecessary.
The density of the image forms during the development step. Normal fixing and a Permawash bath ought to have no effect on the image density or the formation of any spots of low density you see.
But such spots are exactly what we’d expect to see if air bubbles adhered to the film during some part of the development, especially in the early stage.
I’ve found that soaking every film in a water bath and swishing it about to ensure that the film is fully wetted before beginning the development step generally prevents the formation of air bubbles on film.
My experience is that several potential problems are eliminated by soaking all films: B&W, color negative, and color transparency, for several minutes in tempered water prior to the developing step.
My comments are geared to tray development, but the same ideas apply to sheet films developed in tanks.
Last edited by Ian C; 10-02-2011 at 02:16 PM. Click to view previous post history.
Also, if you are tray developing, it’s best to keep the film emulsion-up. If you leave it emulsion-down air bubbles can get trapped underneath and unable to escape and float up to the surface of the developer.
I pre-soak for about 5 minutes, hc110 1:90 for 8 minutes, stop 3/4 strength for 1 minute, fixer at film strength for 5 minutes, permawash for 5 minutes, archival film washer for 30 minutes, distilled water and LFN. Here is an example:
You’ve shown a short somewhat irregular line. Obviously, it’s not an air bubble.
Since the line is dark and you described these as” little spots of less density”, I presume the negative has been reversed to positive.
Given the shape, I wonder about the size. Might it be about the size of a tiny fiber from clothing?
I’m thinking not of threads, which are relatively huge, but rather the very tiny fibers that we can sometimes barely see in beam of sunlight on the surface of, say, a cotton or cotton-polyester blend shirt. I can’t see them unless I’m wearing reading glasses.
I’m wearing such a shirt now and can barely see many fibers that I’d estimate are 0.0001” or less in diameter and possibly 0.020” or somewhat longer. If it weren’t for the beam of glancing sunlight I probably couldn’t see them at all.
Film can be much like a magnet while we’re loading holders in the dark. That will draw almost any particles to it.
The fibers I’m seeing are almost translucent. Something like that might well correspond to what you’re seeing.
If there were only few here and there, the idea of stray fibers might make sense.
If there are a great number of them, then I’d reject the idea.
Possibly someone else has a better explanation.
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You really think it could be from fibers so small and fine that light could get through it but not all the way through it? It's not as though the negatives are littered with these specks, but I have been noticing them a bit more. My film loading area has been more dusty than usual. They are darker spots in the print and lighter on the negative.
Sometimes I find annoying spots on my negatives and then realize those are just birds in the sky. Stupid birds, they ruin my negatives.
I like my film stirred, not shaken.
Birds are welcome to be present in my negatives, random spots are not welcome.
If the spots (more of a line in the example shown) are the result of bird flight paths, then the birds must have been darker colored than the surrounding sky (unless they were in silhouette). This is possible, but is something that you should have noticed just before shooting. If this is the case, you need only wait for a lull in the action and then shoot without the bird blurs.
I did some spotting on a 16” x 20” print from 4” x 5” T-Max 100 negative last night. It’s an early morning view of trees, beach, and marsh grass looking out across Lake Erie towards the distant shore of Ontario.
The negative has a single small defect in the sky area similar to what you showed. It prints as a slightly curved line of moderately greater density than the sky. If it were lighter than the sky it would be easy to spot dye it to match the surrounding area.
The edges are somewhat fuzzy. It’s not black and that means that the image of the line on film is not transparent, just lower density than the surrounding area. It was most definitely not a bird as I made sure that no birds were flying across the scene before shooting.
It’s just enough to be annoying on close inspection. If it was over a darker element, it wouldn’t be noticeable.
On the print, the line is about 4.5mm long and 0.3mm in width. I’m nearly certain that it was caused by the shadow of a micro fiber that had clung to the film during exposure. The magnification of the projection was about 4.7X, so the image of the line on film is about 0.97mm long and 0.06mm in width (or 0.0025” wide x 0.038” long).
No matter how careful we are, sometimes particles of various types stick to sheet films or the holders, or dark slides. There’s no escaping handling sheet films. Particle contamination can be minimized by careful housekeeping in the film loading area and cleaning of the holders. Unfortunately, we can’t totally eliminate the problem.
We all know from observing a shaft of sunlight in a darker room, even one that is scrupulously clean, that there are always visible particles floating in the air. These can adhere to films and cast their shadows during exposure.
I have seen these artifacts on my sheet film negatives occasionally and compared their size and shape to the fibers mentioned in post #5. They seem to match.
One trick that I’d read about years ago might help. Some folks run a room vaporizer for a few minutes in the film loading area to settle dust and help eliminate the static charge that draws particles to the film.
I’ve though of, but not tried, the idea of using a grounding strap that fastens around the wrist with a conducting wire clipped to a bare metal water faucet or the metal case of an electrical outlet to ground us while we load sheet film into holders.
The idea is that any static charge we generate through friction: tearing open a sheet film packet, sliding the films out of the packet, sliding the films into the holder, etc. are discharged to ground so that no attractive charge forms in the first place. Such grounding straps are ready made and inexpensive. They can be bought at Radio Shack or other electronic supplies stores.
We might also place the holders on an aluminum cookie-baking sheet with a length of copper wire and a couple of alligator clips to connect the sheet to a convenient source of ground. Whether these steps help can only be determined by trying them.
I’m not aware of any film manufacturing errors or processing errors that would cause these marks on films. That these occur almost exclusively with sheet films and not roll films lends credence to their being caused by very small fibers sticking to the emulsion during exposure.
This can happen to a roll film, but only rarely. If the film chamber of a roll film camera is allowed to get contaminated with dust and particles, some of them can find their way to the film and cast shadows during exposure. But a roll film camera whose film chamber is brushed and blown out regularly rarely accumulates particles to cause the problem.
Last edited by Ian C; 10-03-2011 at 12:34 PM. Click to view previous post history.
Reason: line spacing
It looks to me like the emulsion contacted something possibly when wet and was "abraided". Try looking at it on an angle to see what the film surface looks like.